Morsi himself said at a rally at Cairo University this week, “We will not accept any alternative to Shari'ah... The Qu'ran is our constitution and it will always be so.”

But Morsi is running so far only in fourth place, in a field of 13 candidates whose first challenge will come during the May 23-24 polls. Ahead of him in popularity thus far are two former regime candidates and Abdel-Moneim Abolfotoh, a more moderate Islamist.

Abolfotoh, who was once a member of the Brotherhood, left the organization after he was blocked from running for president. He has said that a Christian has the right to be president, and that books promoting atheism should not be censored, is also supported by the more hard-line Salafists.

The harder-line Muslim Brotherhood leadership, rejected by its Salafist Islamic colleagues, has become much bolder since gaining control over the parliament.

The party demanded as the majority in parliament that the military allow it to form the next government.

The Brotherhood faction also balked at a World Bank loan taken by the parliament to improve the country's broken sewage system, citing the interest involved, forbidden under Shari'a law.

The party has also called on the government to revoke a Mubarak-era law to allow women to seek a divorce from their husbands in Islamic courts.